Insect demonstrating natural selection (4)
I believe the answer is:
gnat
'insect' is the definition.
(I know that gnat is a type of dipteran)
'demonstrating natural selection' is the wordplay.
'GNAT' is hidden in amongst the letters.
However, I am not sure how the hidden word is indicated.
Can you help me to learn more?
(Other definitions for gnat that I've seen before include "Two-winged fly" , "mozzie" , "Small biter" , "annoying flier" , "Small fly that bites" .)